Known variable force suspension systems include variable force shock absorbers and/or struts (dampers) that provide suspension damping forces at a magnitude controllable in response to commands provided by a suspension system controller. Some systems provide control between two damping states and others provide continuously variable control of damping force. Example systems are described in U.S. Pat. Nos. 5,235,529, 5,096,219, 5,071,157, 5,062,657, 5,062,658, all assigned to the assignee of this invention and the disclosures of which are incorporated herein by reference.
Many variable force dampers use a damping fluid that is sensitive to changes in ambient temperature. Typical damping fluids exhibit an increase in viscosity as the temperature falls below a certain level, for example, below -20 degrees C. As the viscosity of the fluid increases, the force versus relative velocity performance profile of the damper changes, resulting in increased damping force from the damper for a given relative velocity. This change in performance profile of the damper can be noticed by the vehicle operator in the form of increased road and suspension noise and a selective decrease in ride comfort.